Organic electroluminescent device and fabrication methods thereof

Abstract

An organic electroluminescent device is disclosed. A substrate comprises a control area and a sensitive area. A switch device and a driving device are disposed overlying the control area. A photo sensor is disposed overlying the sensitive area, wherein the photo sensor is a thin film transistor. An OLED element is disposed in the sensitive area and illuminating to the photo sensor. A capacitor coupled to the photo sensor and the driving device. A photo current corresponding to a brightness of the OLED element is generated by the photo sensor responsive to the OLED element illuminating the photo sensor such that a the voltage of the capacitor is adjusted by the photo current to control the current passing through the driving device, thus changing the illumination of the OLED element.

1 . An organic electroluminescent device, comprising: 
 a pixel element comprising:    a substrate, comprising a control area and a sensitive area;    a switch device and a driving device overlying the control area;    a photo sensor overlying the sensitive area, wherein the photo sensor is a thin film transistor; and    an OLED element disposed in the sensitive area and illuminating to the photo sensor; and    a capacitor coupled to the photo sensor and the driving device;    wherein a photo current corresponding to a brightness of the OLED element is generated by the photo sensor responsive to the OLED element illuminating the photo sensor such that a the voltage of the capacitor is adjusted by the photo current to control the current passing through the driving device, thus changing the illumination of the OLED element.    
   
   
       2 . The organic electroluminescent device as claimed in  claim 1 , wherein the switch device and the driving device are top gate transistors.  
   
   
       3 . The organic electroluminescent device as claimed in  claim 1 , wherein the photo sensor is a polysilicon thin film transistor.  
   
   
       4 . The organic electroluminescent device as claimed in  claim 3 , wherein the polysilicon thin film transistor comprises: 
 a buffer layer overlying the substrate;    a photo sensor active layer, comprising a source, a drain and a channel therebetween, overlying the buffer layer;    a dielectric layer overlying the photo sensor active layer; and    a photo sensor gate overlying the dielectric layer, wherein the photo sensor gate is transparent.    
   
   
       5 . The organic electroluminescent device as claimed in  claim 4 , wherein the photo sensor active layer comprises polysilicon, and the photo sensor gate comprises indium tin oxide, ITO or indium zinc oxide, IZO.  
   
   
       6 . The organic electroluminescent device as claimed in  claim 4 , wherein the switch device has a first active layer, the driving device has a second active layer, and the photo sensor active layer, the first active layer and the second active layer are formed of the same layer.  
   
   
       7 . The organic electroluminescent device as claimed in  claim 1 , further comprising: 
 a first active layer disposed in the switch device;    a second active layer disposed in the driving device;    a photo sensor active layer disposed in the photo sensor;    a gate dielectric layer disposed overlying the first, the second active layers and the photo sensor active layer;    first and second gates disposed on the gate dielectric layer overlying the control area, wherein the first gate is in the switch device, and the second gate is in the driving device;    a dielectric layer at least covering the first gate, the second gate, and the gate dielectric layer; and    a photo sensor gate overlying the dielectric layer in the sensitive area.    
   
   
       8 . The organic electroluminescent device as claimed in  claim 7 , wherein the dielectric layer and the gate dielectric layer further comprise a plurality of openings, exposing the first and second gates and a portion of the first and second active layers, and the openings are filled with conductive contacts.  
   
   
       9 . The organic electroluminescent device as claimed in  claim 8 , further comprising: 
 a passivation layer disposed overlying the conductive contacts and the dielectric layer;    a first OLED electrode overlying the planarization layer;    an organic light emitting layer disposed on the first electrode; and    a second OLED electrode disposed overlying the organic light emitting layer, wherein the first electrode, the organic light emitting layer and the second electrode constitutes the OLED element.    
   
   
       10 . The organic electroluminescent device as claimed in  claim 1 , further comprising: 
 a display panel, wherein the pixel element is arranged in an array of pixel elements of the display panel.    
   
   
       11 . The organic electroluminescent device as claimed in  claim 10 , further comprising an electronic device, wherein the electronic device comprises: 
 the display panel; and    an input unit coupled to the display panel and operative to provide input to the display panel such that they display panel displays images.    
   
   
       12 . The organic electroluminescent device as claimed in  claim 11 , wherein the electronic device is a mobile phone, digital camera, PDA (personal digital assistant), notebook computer, desktop computer, television, car display, or portable DVD player.  
   
   
       13 . An organic electroluminescent device, comprising: 
 a pixel element comprising:    a substrate, comprising a control area and a sensitive area;    a switch device and a driving device overlying the control area;    a photo sensor overlying the sensitive area; and    an OLED element disposed in the sensitive area and illuminating to the photo sensor; and    a capacitor coupled to the photo photo sensor and the driving device;    wherein a photo current corresponding to a brightness of the OLED element is generated by the photo sensor responsive to the OLED element illuminating the photo sensor such that a the voltage of the capacitor is adjusted by the photo current to control the current passing through the driving device, thus changing the illumination of the OLED element,    wherein the switch device, the driving device and the photo sensor are top gate transistors,    wherein the switch device, the driving device, and the photo sensor have active layers of the same layer.    
   
   
       14 . A method for forming an organic electroluminescent device, comprising: 
 providing a substrate, comprising a control area and a sensitive area;    forming an active layer overlying the control area and the sensitive area of the substrate;    patterning the active layer to form first and second active layers in the control area, and a photo sensor active layer in the sensitive area;    forming a gate dielectric layer overlying the active layer and the sensitive area of the substrate;    forming a conductive layer on the gate dielectric layer;    patterning the conductive layer to form first and second gates in the control area;    forming a dielectric layer at least covering the first gate, the second gate and the gate dielectric layer;    forming a photo sensor gate on the dielectric layer overlying the sensitive area; and    forming an OLED element overlying a portion of the control area and the sensitive area.